A voltage regulator is an electrical circuit that maintains a constant voltage. Voltage regulators require high efficiency and reliability during full load and light load conditions. FIG. 1 illustrates a prior art multiphase voltage regulator 10. Multiphase voltage regulator 10 includes a microcontroller unit (MCU) 100 coupled to the main MCU 114 and to a pulse width modulation (PWM) integrated circuit (IC) 102 in turn coupled to a set of n current-drivers 104 (104a-104n). Each of the n current-drivers 104 includes a voltage driver D (Da-Dn) controlling high-side (HS) and low-side (LS) MOSFETs (HSa/LSa-HSn/LSn), which drives an inductor L (La-Ln). Each of the inductors L are tied together to drive a capacitor C and load 116 coupled in parallel. The PWM IC 102 includes an oscillator 106, data I/O and a reference voltage (Vref) circuit 108, and an analog comparator 110, each coupled to PWM control logic 112.
FIG. 2 illustrates prior art multiphase PWM waves generated by the PWM IC 102. The PWM waves are phase shifted by 2π/n (n being phase number). In the 6-phase case, the PWM waves are phase shifted by 2π/6 or 60 degrees. The 6-phase case achieves a fixed Vout, and controls the PWM duty to Vout/Vcc. If Vcc=12V and Vout=1.2V, then the PWM duty is 10%. Each PWM wave drives a respective current-driver 104, causing it to source a current with a respective phase corresponding to the PWM wave. That is, when the PWM wave is High, the corresponding HS MOSFET turns ON and the corresponding LS MOSFET turns OFF. Current flows from Vcc through the inductor L to the load 116. Ldi/dt1=Vcc−Vout. When the PWM wave is Low, the corresponding HS MOSFET turns OFF and the corresponding LS MOSFET turns ON. The current flows from GND through the inductor L to the load 116. Ldi/dt2=Vout. Hence, the duty=Vout/Vcc=dt1/(dt1+dt2).
The prior art voltage regulator 10 uses a hardware-designed PWM IC 102 to control output current. Accordingly, adaptive control is difficult. For example, changing the number of phases requires switching out the PWM IC 102 and possibly changing the entire design, which is inconvenient and costly.